Resilient Power Supplies (RPSs) provide back-up electrical power in systems such as Personal Computers (PCs), enabling orderly shutdown during an Alternating Current (AC) power outage. There are many ways of providing resiliency. The common methods are to attach an Uninterruptible Power Supply (UPS) to the AC input of the PC power supply or to tap the high voltage point of the PC power supply to charge and discharge a battery. However, these methods are bulky and expensive.
For example, a UPS can be bulky, depending on the total power requirements and the length of back-up time required by the load, and adds additional cost and complexity to a system. Further, signaling between a UPS and a PC requires use of an externally exposed interface such as a Universal Serial Bus (USB) in accordance with the USB Specification Rev. 2.0 (published December 2000) or an industry standard (e.g., RS-232) interface. Use of these interfaces allows control when system software is operating, but the interfaces are inoperative when the system is suspended, making coordination between an operating system (OS) running on the system and the UPS problematic.
A typical RPS architecture includes an internal power supply with a high-voltage mid-point to both charge and discharge an associated Safe Extra Low Voltage (SELV) battery (e.g., corresponding to an International Electrotechnical Commission (IEC) standard). Such a high-voltage tap architecture for both charging/discharging the battery has the disadvantage of requiring electrical isolation between the high-potential end and battery portions of the circuit, due to safety considerations. Thus transformers are used for the charging portion of the RPS, making it bigger in size, heavier and also more expensive.
A need thus exists to provide resilient power to a system that overcomes these problems.